Demographic effects of live shearing on a guanaco population

Abstract

Live shearing of wild guanacos (Lama guanicoe) is promoted as an alternative to livestock production and a conservation tool in the Argentinean Patagonia. However, biological sustainability of guanaco shearing has not been evaluated. We studied movements, population trends, survival, and yearling recruitment of guanacos, comparing sections with and without roundups on a Patagonian sheep ranch. A total of 2900 guanaco captures occurred in 10 roundups from 2003 to 2007. We estimated guanaco density and yearling/adult ratios with line transect surveys. We evaluated if guanacos left the section with roundups through direct observation of tagged guanacos and radiotelemetry. We estimated survival rate of shorn guanacos using 1334 capture–recapture histories. Guanaco population trends in sections with and without roundups were stable throughout a normal-rainfall period and declined during the drought that followed. Roundups were followed by temporary declines in density estimates probably associated with altered guanaco behavior. Tagged guanacos were rarely observed outside the section with roundups and none of the radiocollared guanacos permanently left the section. We estimated a constant annual survival rate for shorn guanacos (82% SE = 0.01) that was independent of sex and age. Yearling proportions declined in the section with roundups 2–3 months after summer roundups. Our results suggest that, under conditions similar to those of our study (i.e. following animal welfare practices in a ranch with moderate livestock densities and sections without livestock), live shearing would not imperil wild guanacos if roundups were conducted in spring and during normal-rainfall periods.